Question 1

What is a renewable energy certificate, and does buying green electricity work?

Accepted Answer

A certificate proving that a unit of electricity was generated from a renewable source — and whether buying one changes anything depends on a concept called **additionality**, which is where most green tariffs fall down.

**The physical reality first.** Electricity from all sources mixes on the grid. **The electrons reaching your home are not traceable**, and no supplier can send you specifically renewable electricity. Green tariffs are therefore an accounting arrangement, not a physical one — which is not a criticism in itself, since accounting is how the system works.

**How the certificates operate.** In the UK, a generator receives a **REGO** — Renewable Energy Guarantee of Origin — for each unit generated. Suppliers buy REGOs to match the electricity they sell, and can then describe that electricity as renewable.

**The problem.** REGOs can be bought and sold **separately from the electricity itself**. A supplier can buy ordinary grid electricity and separately buy certificates from a wind farm that would have operated regardless, then market the result as a green tariff. The wind farm was built and is running either way; the certificate has changed nothing physical.

Because certificates have historically been cheap relative to the electricity, the cost of making a tariff "green" this way is small — which is why so many tariffs are.

**Additionality** is the test: **did your purchase cause additional renewable generation to exist?** Buying a certificate from an existing plant fails it. Regulators and consumer bodies have repeatedly criticised green tariffs on these grounds.

**What does have a stronger claim:**

**Power purchase agreements**, where a long-term contract underwrites the finance for a specific new project. This genuinely enables generation that would not otherwise be built.

**Suppliers that own and build their own generation.**

**Tariffs that publish the specific source** of their supply, rather than a certificate portfolio.

**Generating your own**, which is unambiguously additional.

**The counter-argument**, fairly stated: demand for certificates creates a revenue stream and a signal, and a market with no mechanism to express preference would be worse. The effect is real but far weaker than the marketing implies.

Question 2

What is curtailment, and why are wind farms paid to stop?

Accepted Answer

Curtailment is reducing generation below what a plant could produce — and wind farms are compensated for it because the grid physically cannot move the electricity to where it is needed, not because

Question 3

Do sustainability certifications mean anything?

Accepted Answer

It depends entirely on what is certified, by whom, and against what standard — and the range runs from rigorous third-party audit to a logo a company designed itself. The questions that separate

Question 4

Why is energy storage the hard problem for renewables?

Accepted Answer

Because electricity grids must balance supply and demand continuously and instantaneously, and the main renewable sources produce power when conditions allow rather than when it is needed. The

Question 5

What are scope 1, 2 and 3 emissions?

Accepted Answer

A classification of an organisation's greenhouse gas emissions by where they occur relative to the organisation, established by the Greenhouse Gas Protocol and now the standard framework for

Question 6

What is greenwashing and how do I spot it?

Accepted Answer

Greenwashing is presenting something as more environmentally responsible than it is. It ranges from outright false claims to technically true statements arranged to mislead, and the second is far

Question 7

Why do wind turbines stand still?

Accepted Answer

For several quite different reasons, and "there is no wind" is only one of them — the others are more interesting and are routinely misread as evidence that the technology does not work. The reasons,

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